PHAntom Viewer is an interactive display of known asteroids and comets designated as
"Potentially Hazardous Objects." This means
that each object is on an orbit which takes it within a very close approach to Earth at some point in time and, in
the case of an impact, carry the potential to cause significant or catastrophic damage.

Orbital information on more than 1,400 "PHOs" and the planets are obtained from the NASA/Jet Propulsion Laboratory
periodically to keep the list current. Orbits as portrayed are static and effects from gravitational influences, such as
a close encounter with Earth or Jupiter, have not yet been implemented. While planet and asteroid orbits are to scale,
the planet sizes and Moon orbit have been exaggerated.

This is built as a WebGL experiment using Three.js and is expected
to work in the latest versions of Google Chrome, Firefox, & Internet Explorer 11.

Asteroids and comets that come within the configured maximum distance window (default of .15 AU, or 22.5 million kilometers)
are shown. They are colored from green to red as the object approaches Earth, with bright red indicating a very
close approach. Objects within the distance window will be displayed in the list on the top right.

Click 'Start' to begin the animation, then control with 'Pause' and 'Resume'.

To move to a specific date, set the 'Start Date', then click 'Reset to Start Date'.

Adjust the animation speed using 'Animation Speed'.

Use 'Targeted Planet' to change which planet is being watched. Note that the asteroid list is optimized
for Earth resulting in possibly incomplete lists for other planets.

View Controls:
PHAntom Viewer uses mouse and keyboard based navigation controls, similar to those in Google Earth.

Rotating: Rotate the scene by left-clicking and dragging with the mouse

Pitch/Roll: Control the pitch & roll of the scene by holding down shift while left-clicking and
dragging with the mouse.

Panning: Pan the scene (offsetting the planet from the center, similar to turning your head away from
the object of focus) by holding down Ctrl while left-clicking and dragging with the mouse.

Zooming: Zoom either with the scroll-wheel or by right-clicking and dragging the mouse up or down.